src/backend/libpq/pqsignal.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * pqsignal.c
   4  *        reliable BSD-style signal(2) routine stolen from RWW who stole it
   5  *        from Stevens...
   6  *
   7  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  *
  11  * IDENTIFICATION
  12  *        $PostgreSQL$
  13  *
  14  * NOTES
  15  *              This shouldn't be in libpq, but the monitor and some other
  16  *              things need it...
  17  *
  18  *      A NOTE ABOUT SIGNAL HANDLING ACROSS THE VARIOUS PLATFORMS.
  19  *
  20  *      pg_config.h defines the macro HAVE_POSIX_SIGNALS for some platforms and
  21  *      not for others.  This file and pqsignal.h use that macro to decide
  22  *      how to handle signalling.
  23  *
  24  *      signal(2) handling - this is here because it affects some of
  25  *      the frontend commands as well as the backend server.
  26  *
  27  *      Ultrix and SunOS provide BSD signal(2) semantics by default.
  28  *
  29  *      SVID2 and POSIX signal(2) semantics differ from BSD signal(2)
  30  *      semantics.      We can use the POSIX sigaction(2) on systems that
  31  *      allow us to request restartable signals (SA_RESTART).
  32  *
  33  *      Some systems don't allow restartable signals at all unless we
  34  *      link to a special BSD library.
  35  *
  36  *      We devoutly hope that there aren't any systems that provide
  37  *      neither POSIX signals nor BSD signals.  The alternative
  38  *      is to do signal-handler reinstallation, which doesn't work well
  39  *      at all.
  40  * ------------------------------------------------------------------------*/
  41
  42 #include "postgres.h"
  43
  44 #include <signal.h>
  45
  46 #include "libpq/pqsignal.h"
  47
  48
  49 #ifdef HAVE_SIGPROCMASK
  50 sigset_t        UnBlockSig,
  51                         BlockSig,
  52                         AuthBlockSig;
  53 #else
  54 int                     UnBlockSig,
  55                         BlockSig,
  56                         AuthBlockSig;
  57 #endif
  58
  59
  60 /*
  61  * Initialize BlockSig, UnBlockSig, and AuthBlockSig.
  62  *
  63  * BlockSig is the set of signals to block when we are trying to block
  64  * signals.  This includes all signals we normally expect to get, but NOT
  65  * signals that should never be turned off.
  66  *
  67  * AuthBlockSig is the set of signals to block during authentication;
  68  * it's essentially BlockSig minus SIGTERM, SIGQUIT, SIGALRM.
  69  *
  70  * UnBlockSig is the set of signals to block when we don't want to block
  71  * signals (is this ever nonzero??)
  72  */
  73 void
  74 pqinitmask(void)
  75 {
  76 #ifdef HAVE_SIGPROCMASK
  77
  78         sigemptyset(&UnBlockSig);
  79
  80         /* First set all signals, then clear some. */
  81         sigfillset(&BlockSig);
  82         sigfillset(&AuthBlockSig);
  83
  84         /*
  85          * Unmark those signals that should never be blocked. Some of these signal
  86          * names don't exist on all platforms.  Most do, but might as well ifdef
  87          * them all for consistency...
  88          */
  89 #ifdef SIGTRAP
  90         sigdelset(&BlockSig, SIGTRAP);
  91         sigdelset(&AuthBlockSig, SIGTRAP);
  92 #endif
  93 #ifdef SIGABRT
  94         sigdelset(&BlockSig, SIGABRT);
  95         sigdelset(&AuthBlockSig, SIGABRT);
  96 #endif
  97 #ifdef SIGILL
  98         sigdelset(&BlockSig, SIGILL);
  99         sigdelset(&AuthBlockSig, SIGILL);
 100 #endif
 101 #ifdef SIGFPE
 102         sigdelset(&BlockSig, SIGFPE);
 103         sigdelset(&AuthBlockSig, SIGFPE);
 104 #endif
 105 #ifdef SIGSEGV
 106         sigdelset(&BlockSig, SIGSEGV);
 107         sigdelset(&AuthBlockSig, SIGSEGV);
 108 #endif
 109 #ifdef SIGBUS
 110         sigdelset(&BlockSig, SIGBUS);
 111         sigdelset(&AuthBlockSig, SIGBUS);
 112 #endif
 113 #ifdef SIGSYS
 114         sigdelset(&BlockSig, SIGSYS);
 115         sigdelset(&AuthBlockSig, SIGSYS);
 116 #endif
 117 #ifdef SIGCONT
 118         sigdelset(&BlockSig, SIGCONT);
 119         sigdelset(&AuthBlockSig, SIGCONT);
 120 #endif
 121
 122 /* Signals unique to Auth */
 123 #ifdef SIGQUIT
 124         sigdelset(&AuthBlockSig, SIGQUIT);
 125 #endif
 126 #ifdef SIGTERM
 127         sigdelset(&AuthBlockSig, SIGTERM);
 128 #endif
 129 #ifdef SIGALRM
 130         sigdelset(&AuthBlockSig, SIGALRM);
 131 #endif
 132 #else
 133         /* Set the signals we want. */
 134         UnBlockSig = 0;
 135         BlockSig = sigmask(SIGQUIT) |
 136                 sigmask(SIGTERM) | sigmask(SIGALRM) |
 137         /* common signals between two */
 138                 sigmask(SIGHUP) |
 139                 sigmask(SIGINT) | sigmask(SIGUSR1) |
 140                 sigmask(SIGUSR2) | sigmask(SIGCHLD) |
 141                 sigmask(SIGWINCH) | sigmask(SIGFPE);
 142         AuthBlockSig = sigmask(SIGHUP) |
 143                 sigmask(SIGINT) | sigmask(SIGUSR1) |
 144                 sigmask(SIGUSR2) | sigmask(SIGCHLD) |
 145                 sigmask(SIGWINCH) | sigmask(SIGFPE);
 146 #endif
 147 }
 148
 149
 150 /* Win32 signal handling is in backend/port/win32/signal.c */
 151 #ifndef WIN32
 152
 153 /*
 154  * Set up a signal handler
 155  */
 156 pqsigfunc
 157 pqsignal(int signo, pqsigfunc func)
 158 {
 159 #if !defined(HAVE_POSIX_SIGNALS)
 160         return signal(signo, func);
 161 #else
 162         struct sigaction act,
 163                                 oact;
 164
 165         act.sa_handler = func;
 166         sigemptyset(&act.sa_mask);
 167         act.sa_flags = 0;
 168         if (signo != SIGALRM)
 169                 act.sa_flags |= SA_RESTART;
 170 #ifdef SA_NOCLDSTOP
 171         if (signo == SIGCHLD)
 172                 act.sa_flags |= SA_NOCLDSTOP;
 173 #endif
 174         if (sigaction(signo, &act, &oact) < 0)
 175                 return SIG_ERR;
 176         return oact.sa_handler;
 177 #endif   /* !HAVE_POSIX_SIGNALS */
 178 }
 179
 180 #endif   /* WIN32 */